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ads4149 spi Interface

Fred L Skalka
Intellectual 260 points

Other Parts Discussed in Thread: ADS4149

I would like to daisy chain the SPI interface for four ADS4149 ADCs.  When I disabel SEN, is the internal SPI interface put in bypass (i.e. SDIN is passed directly to SDOUT) or is the whole interface disabled (i.e. SDOUT is set to a default level regardless of the value of SDIN).  Of course, this assumes that there is proper activity on SCLK.

  • 0
    TI__Genius 17470 points

    Hi Fred,

    When SEN is disabled, the SPI interface is NOT put into a bypass mode. The OVR_SDOUT pin only has two states, which are dictated by bit 0 of SPI register 0x00. When the READOUT bit is set to 0, the pin functions as an over-voltage indicator (an output). When READOUT is set to 1, the OVR_SDOUT pin is used as a READOUT pin with a default state of low when a read is not occuring, this does not have a high-Z output. The part cannot be left in READBACK mode constantly because this disables writing to the registers.

    So SCLK and SDATA can be shared between all four ADCs. Each ADC will require a separate SEN signal. OVR_SDOUT cannot be combined, so each ADC would need a separate OVR_SDOUT connection.

    Regards,
    Matt Guibord